A common problem encountered by mechanics and others when using pliers is that it is often difficult to cause the jaws thereof to grip an object placed therein with sufficient force so that the jaws of the pliers do not slip with respect to the object, when a user attempts to move the object by way of the pliers. A familiar example is, for instance, encountered when pliers are applied to a the head of a bolt, which bolt is firmly secured in a nut. Even in the case in which the head of the bolt is easily accessible, it is often times very difficult to apply sufficient force to the handles of a typical pliers so that the head of the bolt is gripped firmly enough in the jaws of the pliers to allow it to be turned by the user, by way of the pliers. The problem is even more emphasised when the head of the bolt, or other object, is difficult to access. For instance, where a user is attempting to repair a plumbing pipe which is located in a cabinet, and where the only access to the pipe is from the back of the pipe, as viewed by the user from outside of the cabinet. In such a case it is often possible for a user to manipulate the pliers into a suitable position, but impossible for the user to reach the handles thereof in a manner which allows the user to impart sufficient force thereto, which force is translated into an object gripping force at the jaws of the pliers. As a result the pliers slip when a user attempts to turn the pipe fitting by way of the pliers.
In answer to the identified, or related, problem various inventors have developed various systems which aid a user of pliers in the application of required gripping force, via the jaws of pliers, to an object which the user thereof intends to move, by way of the pliers. In particular, a patent to Mellum, U.S. Pat. No. 1,294,689, teaches a pliers which comprises handles and jaws functionally interconnected very near the jaws so that when the handles thereof are forced together, the jaws thereof are likewise forced together. The basic pliers can be visualized as comprised of two basic elements, each having a relatively long handle region at one end thereof, and a relatively short jaw region at the other end thereof, with an angled region between the relatively long handle and relatively short jaw regions. The two elements are pivotally interconnected with one another near the jaws thereof and in the angled regions so as to form an "X" shaped formation therebetween. It is also noted that when assembled into a pliers the angled region of one basic element is oriented to project at an acute angle upward, and the angled region of the other basic element is oriented so as to project at an acute angle downward, when both basic elements are viewed with their relatively long handle regions oriented one above the other, essentially horizontally and in side elevation from a distance perpendicularly removed therefrom. The Mellum invention also comprises a third element applied to the pliers, which third element is pivotally interconnected with the handle of one of the two plier basic elements at some distance from the pivotal connection between the two basic elements. The third element has present, at its extent which projects nearest the jaw region of the pliers, teeth, which teeth are complimentary to teeth present on the outer edge of the jaw which is associated with the handle of the pliers to which the third element is not pivotally interconnected. In use one can grip the handles of the pliers and apply force thereto, thereby causing the handles to move toward one another, and by the action of the pliers, also cause the jaws thereof to move closer to one another, or if in contact with each other or an object placed therebetween, cause increased force to be applied thereto between the respective jaws. The teeth on the third element can then be caused to interact with the teeth on the edge of the jaw which is associated with the handle to which the third element is not pivotally interconnected, to retain the pliers in the position attained by user applied force. While the Mellum invention does not provide a means by which a user thereof can more easily apply the force which is required to cause the handles of the pliers involved to move toward one another, it does provide a locking mechanism of sorts which allows a user to position the pliers and cause them to retain said position without sustained effort, on the part of the user.
A British Patent, Number 18,694, teaches a system somewhat similar to the pliers system taught in Mellum, but the two basic elements are relatively straight. Near the jaw ends of the basic elements, however, the two basic elements are pivotally interconnected so that a user thereof can effect action of the combined system similar to that possible by a user of the Mellum invention. The difference between the Mellum and the British inventions is found in the way that the positioning of the two basic elements is secured after a user applied force causes the handles of the British invention to move toward one another which, by plier action, causes the jaws thereof to move closer together, or provide increased contact force therebetween, or provide increased gripping force to an object positioned within the jaws. The British invention teaches that a third element should be pivotally interconnected with one of the handles of the pliers much as is taught in the Mellum Patent, however, the British Patent teaches that a fourth element should also be present and pivotally interconnected with the second handle of the pliers. The third element is designed so that it can pivot to a position colinear with the handle to which it is pivotally interconnected, during initial use of the invention. The British Patent also teaches the presence of fifth and sixth elements. These elements are present on the ends of the handles of the invention. In use a user forces the handles sufficiently close to one another so that the fifth and sixth elements can be caused to interact and fix the handles in a stable position with respect to one another. The third and fourth elements of the British invention are then pivoted into cooperative position with respect to one another and made to interact so as to allow a user thereof to cause the handles of the invention to move even closer to one another. The interaction of the fifth and sixth elements secure the handles of the system allow the interaction between the third and fourth elements to be initiated. By fixing the relative positioning of the handles of the invention, the fifth and sixth elements allow a user the freedom to focus attention on the task of manipulating the fourth and fifth elements into a functionally cooperative interaction.
Another patent, U.S. Pat. No. 2,822,715 to Raimondi teaches a different approach to effecting an action which can effectively grip an object within the jaws of a pliers. The Raimondi invention, however, pivotally interconnects the basic elements thereof to one another at a position near the ends of the handles thereof. The jaws of the Raimondi system are located distally from their interconnection point, along the lengths of the basic elements. Projections are present on one of the so pivotally interconnected basic elements which encompasses the first basic element along the sides thereof to a point just short of the jaw region, and a cam-like lever is pivotally interconnected between the projections which further encompasses the first basic element at the top thereof. In use, an object is positioned in the jaws of the Raimondi system and the cam-like lever is caused to rotate, thereby forcing the basic element which is encompassed by the projections and the cam-like lever, closer to the basic element from which the projections originate. When the cam-like lever is sufficiently rotated it will be found to attain a relatively stable position in which it will maintain the relative position of the two basic elements with respect to one another without further user applied force being required. The Raimondi invention also includes an adjustment means by which the distance between the jaws at the initiation of the rotation of the cam-like lever can be set. This allows use of the Raimondi invention with objects of various size.
While the Raimondi invention arguably provides a system which makes it easier for a user to apply force to the jaws of a pliers or the like, via cam-like lever action, it teaches the requirement of a relatively complex, hence expensive, system. In addition, while the Mellum and British Patents teach inventions which can lock a pliers or the like in a certain position once achieved by user applied force, neither provide any mechanism which makes it easier to apply that force to the plier systems thereof, in the first place.
A need exists for a pliers system which is relatively simple in construction, hence economical to produce, and which makes it relatively easier for a user thereof to apply force to the handles of the pliers when the pliers is used to move an object which is positioned and gripped within its jaws. The system should also be applicable to plier-like systems such as tin-snips and channel locks.